The present invention is directed to vacuum or positive pressure seed meters for a seeding machine. Particularly, the invention is directed to controlling the air pressure applied to seed meters of a seeding machine.
Modern seeding machines use plural seed meters spaced apart along a pneumatic manifold corresponding to planting rows. One such seed meter is disclosed, for example, in U.S. Pat. No. 5,170,909 assigned to the assignee of the present invention. Sophisticated seed metering systems for controlling the rate at which seeds are planted use air pressure to control the application of seed to the ground. In some systems, positive air pressure is used. In other systems, negative air pressure in the form of a vacuum is used to meter the seed.
Positive or negative air pressure is generated by an air pump in the form of a fan. This air pressure from the air pump is directed to a pneumatic manifold. The pneumatic manifold in turn is pneumatically coupled to individual seed meters by hoses.
The air pressure supplied to different row seed meters is not identical. Such a condition results in uneven seed meter performance, possibly resulting in variations in row-to-row seed population and/or seed spacing along the rows. The positive or negative air pressure is highest at those seed meters pneumatically closest to the source of pressurized air or vacuum.
The present inventors have recognized the desirability of proving an air pressure seed metering system that compensates for variations in air pressure along the pneumatic manifold to ensure a consistent row-to-row seed population and seed spacing along each row.
The present invention provides a pressure control system that is configured to precisely tune positive air pressure or vacuum to pneumatic seed meters that are located along a pneumatic metering manifold.
The system includes pressure control valves pneumatically located at plural seed meters that adjust the air pressure or vacuum at the seed meters. The system can utilize feedback pressure signals from pressure sensors at each meter to equalize positive air pressure or vacuum at the seed meters to ensure consistent row-to-row seed populations. Alternatively, the system could utilize seed population measurement as a feedback signal to adjust control valves.
A seeding machine is provided with a frame having a plurality of pneumatic seed meters. An air pump located on the frame supplies air pressure, positive or negative, depending on the seed meter type, to a pneumatic manifold. The pneumatic manifold in turn is pneumatically coupled to the seed meters by air hoses. Control valves, such as adjustable orifice valves, are pneumatically positioned between the pneumatic manifold and each air connection of the seed meters.
The pneumatic manifold is provided with radially extending tube stubs that are coupled to air hoses. The controllable pneumatic orifices can be connected to the tube stubs, can be connected at a point along the air hose, or can be connected to the seed meter.
The adjustable orifice valve of the invention comprises a substantially enclosed housing having a first air connection and a second air connection with a flow pathway therebetween. One or more baffles are arranged within the housing in the pathway between the air connections. An actuator is mounted to the housing and is operable to position the baffle to a controllable degree between the first and second air connections, to restrict flow through the orifice valve. In one embodiment three baffles are used to form an iris which can increase or decrease the orifice opening between the air connections while maintaining orifice concentricity. In another embodiment a single baffle can be used to close off the orifice in the pathway between the air connections in an eccentric manner.
As an alternative to the separate enclosed housing, the control valve of the invention could be incorporated into the seed meter housing/manifold.